Oxygen content of biomass

These points hold only partially for the production of chemicals from biomass. The smallest part of bulk chemicals consists of unfunctionalized hydrocarbons. Nevertheless, the oxygen content of biomass has to be reduced to the level needed for typical bulk chemicals. Therefore, strategies are strongly needed [7]. 

Important biomass fuel properties for thermochemical conversion processes are reported as proximate and ultimate analyses. The proximate and ultimate analyses for selected biomass feedstocks are presented in Table 33.5. For comparison, the analyses from two selected coal samples are also presented. Biomass generally has a lower energy density than coal, oils, and natural gas it also has higher oxygen content. The higher volatiles and oxygen content of biomass translate into a higher reactivity compared to traditional fossil fuels. In terms of thermochemical conversions, this means that less severe process conditions (lower temperature and shorter residence time) are required for bio-... 

Detoxification methods, pesticide content of fish, environmental analytical and monitoring techniques. (4 Utilization of biomass, drinking water quality, organic contaminants in lakes and rivers, and effect of deforestation on carbon dioxide and oxygen content of air. 

The conversion of biomass to automotive fuels has perhaps received the most attention of any chemical biomass conversion process. One of the most visible technologies under this classification is the aqueous phase reforming (APR) process [35], in which the oxygen content of carbohydrate feedstocks is reduced with in-situ... 

Biomass is predominantly eomposed of biopolymers, for example cellulose, hemieellulose, and lignin. From a molecular viewpoint, converting non-food biomass to liquid fuels is a process of transforming solid-phase macromolecules into liquid-phase small molecules. Simultaneously, it is necessary to reduce the oxygen content of the small molecules to improve the energy density. 

A high aromatics selectivity, however, requires proper catalyst selection. Zhang et al. studied the fast pyrolysis of corncob in absence and presence of a catalyst (ie, ZSM-5) [287]. The presence of the catalyst increased the yields of noncondensable gas, water, and coke, while decreasing the liquid and char yields. The catalyst induced a decrease of the oxygen content of the liquid fraction by more than 25%. These studies indicate the importance of a catalyst during biomass pyrolysis. The most important catalytic parameters affecting the product distribution are pore structure and acid site type. This was demonstrated by testing siUcalite, a material with the same pore structure as ZSM-5 but with intrinsic different acid sites, and siUca-alumina, an amorphous material with Brpnsted acid sites, in the catalytic pyrolysis of... 

Temperature strongly influences the yield distribution and the physical/chemical properties of the products such as carbon content, pH, viscosity, and oxygen content of the bio-oil. The addition of catalysts to the reaction system has been shown to lower the reaction temperature (Mertinkat et al., 1999) and as the thermal degradation reactions of biomass and waste material during pyrolysis are endothermic this can lead to reduced energy demand and operating costs. Reaction temperature is a critical parameter that affects vapor phase catalyzed reactions (Morris et al., 2011). 

The elemental analyzer measures the C, H and N content of biomass upon its combustion at 925°C in a pure oxygen environment by monitoring the volatile compounds (C in CO2, N in N2, H in H2O). The results are reproducible but largely dependent on the growth conditions the solid residue of combustion is ash and contains oxides and salts. Mass fractions of biomass can be expressed as ... 

Hence, the oxygen fraction of biomass is overestimated when calculating/o without taking into account the S fraction. However, experimental values show that the overestimation of the oxygen content is only about 2% as illustrated later on. 

The samples are prepared as for elemental analyses and the moisture content of the sample has to be determined in parallel. The principle of enthalpy of combustion measurement consists of burning a sample in a pure oxygen environment and then measuring the temperature increase of the surrounding water bath [34,43,44]. The ignition is initiated by a copper wire, and the measurements are corrected for moisture content of biomass, nitrous and sulfuric acid formation. A complete description of the measurement instruction can be found in references [28,34]. 

Hydrothermolysis is a specific process developed by Shell for producing an oil-like material, called bio-erude, with a low oxygen content. The process is so called because it involves treatment of the biomass with water at temperatures of 200-330 °C and pressures over 30 bar. Although the proeess is not yet economical it may well be so in the near future as crude oil prices eontinue to rise. 

Fed-batch fermentations with P. oleovorans have been carried out using octa-nol and octanoate as substrate [53]. To ensure high oxygen transfer rates pure oxygen was used. With octanoate as substrate 41.8 g 1 1 biomass with a cellular PHA content of 37 % and a productivity of 0.34 g l"1 were reached. Higher biomass concentrations could not be achieved due to accumulation of the toxic octanoate. 

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